It’s important to choose godparents who can be present at the christening service. Here’s an explanation of why that matters.
Godparents are really important people at a christening. A person can only be an official godparent if they are physically present at the service, since they will make some big promises for and on behalf of the child on the day.
As they are already making promises on behalf of the child, to have another person making promises on their behalf confuses who is making promises on behalf of who! So there is actually no provision in the Church of England for ‘godparents by proxy’.
However, if a special person who you wanted to be a godparent is unable to make it to a christening, there is no reason why they can’t be asked to take on a godparent-like role unofficially, and that kind of relationship can be encouraged throughout the child’s life, but they wouldn’t be entered into the Baptism Register after the christening. If the church has the facilities, they could perhaps be linked via Skype or similar software, so they can still see the service.